Engine having variation volume crank case

ABSTRACT

An engine having a crank case of a variable volume may include a crankshaft that may be disposed in a crank case and may be connected to a piston through a connecting rod, which reciprocate in a cylinder, a balance shaft that may be disposed in the crank case and may be operated by the crankshaft, a chamber that may be extended from the crank case, and a balance weight that may be formed on the balance shaft and selectively opens or closes a fluid communication between the chamber and the crank case according to a position of the piston.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2010-0124949 filed in the Korean Intellectual Property Office on Dec.8, 2010, the entire contents of which is incorporated herein for allpurposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine having a crank case of avariable volume that varies volume of the crank case according tomovements of a piston.

2. Description of Related Art

Illustrated as one example, a blow by gas that escapes through a finegap between a piston and a cylinder is formed during a combustion of anengine, if it is exhausted to the outside, the atmosphere pollution iscaused thereby, and if the blow by gas is inappropriately handled, aninterior pressure of the crank case is increased and the engine can beexploded thereby.

The blow by gas that is formed during the combustion of the engine istransferred to a head cover through a blow by passage that is formed bypenetrating a cylinder block and a cylinder head from the crank case.The blow by gas that flows into the head cover passes a baffle plate tofilter oil of the blow by gas is again supplied to an intake systemthrough a PCV valve (Positive Crank case Ventilation Valve) and abreather, and then it is supplied into the combustion chamber again.

If the blow by gas is not circulated to the intake system to becombusted, the pressure increment of the crank case can cause the engineto be fail. The blow by gas is to be recirculated through a blow bypassage of the cylinder block and the cylinder head between the crankcase and the head cover so as to secure smooth flowing of the blow bygas. For this purpose, it is necessary to enlarge the crank case orwiden a cross-section of the blow by gas passage.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to provide anengine having a crank case of a variable volume having advantages ofvarying a volume according to a movement of a piston to absorb apressure variation.

In an aspect of the present invention, the engine having a crank case ofa variable volume, may include a crankshaft that may be disposed in acrank case and may be connected to a piston through a connecting rod,which reciprocate in a cylinder, a balance shaft that may be disposed inthe crank case and may be operated by the crankshaft, a chamber that maybe extended from the crank case, and a balance weight that may be formedon the balance shaft and selectively opens or closes a fluidcommunication between the chamber and the crank case according to aposition of the piston.

The crankshaft may include a drive gear and the balance shaft mayinclude a driven gear that may be engaged with the drive gear.

The chamber may be fluid-connected to the crank case through an inlet,the balance shaft may be disposed at a side of the inlet, and thebalance weight may be formed to may have a half circle shape along anexterior circumference direction of the balance shaft.

The balance weight may have an equal radial width along the exteriorcircumference of the balance shaft to rotatably contact with the inlet.

The chamber may be disposed in a length direction of the crankshaft tobe connected to the crank case, the inlet may be formed between thechamber and the crank case in a length direction of the balance shaft,and the balance weight may be disposed in a length direction of thebalance shaft corresponding to the inlet.

The fluid communication between the chamber and the crank case may beclosed when the piston may be at a top dead center.

The fluid communication between the chamber and the crank case openswhen the piston may be at a bottom dead center.

In an exemplary embodiment of the present invention, the chamber isformed at one side of the crank case and the chamber communicates withthe crank case through the balance weight, wherein the volume of thecrank case is varied by the movement of the piston such that pressurevariation in the crank case is absorbed. Accordingly, the blow by gascan be effectively recirculated without enlarging the volume of thecrank case or the blow by passage in an exemplary embodiment.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a condition that a piston risesin an engine having a crank case of a variable volume according to anexemplary embodiment of the present invention.

FIG. 2 is a perspective view showing a power delivery structure of acrankshaft and a balance weight of the FIG. 1.

FIG. 3 is a cross-sectional view showing a condition that a pistondescends in an engine shown in the FIG. 1.

FIG. 4 is a perspective view showing a condition that a balance weightis disposed in a chamber.

FIG. 5 to FIG. 8 show operational states of a balance weight in aninlet.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

FIG. 1 is a cross-sectional view showing a condition that a piston risesin an engine having a crank case of a variable volume (for convenience,hereinafter ‘engine’) according to an exemplary embodiment of thepresent invention. Referring to FIG. 1, an engine 1 according to anexemplary embodiment includes a cylinder block 10 having a cylinder 11,a crank case 20 that is connected to a lower portion of the cylinderblock 10, and an oil fan 25 that is connected to a lower portion of thecrank case 20 to supply oil.

The cylinder block 10 can have two cylinders, three cylinders, or fourcylinders depending on the number of the cylinder 11. The multi cylinderengine 1 has its own phase of the piston 12 per cylinder so as tobalance and set combustion order. The inherent movement of the piston 12affects an interior pressure of the crank case 20 or offsets an interiorpressure thereof through the up/down operation of the piston 12.

For example, in a case of 3 cylinder engine, because a crankshaft has aphase difference of 120 degrees, while one piston rises and tow pistonsdescends, a pressure within the crank case fluctuates.

In a case of 2 cylinder engine, there is no phase difference betweencylinders and two pistons respectively moves up and down such that apressure variation is formed as much as a stroke of a piston.

The two cylinder engine is exemplarily described, an engine 1 includes acrankshaft 30 that is disposed in a crank case 20 to be connected to apiston 12 through a connecting rod 13 moving up and down in a cylinder11, and a balance shaft 40 that is disposed in the crank case 20 to berotated by the crankshaft 30.

FIG. 2 is a perspective view showing a power delivery structure of acrankshaft and a balance weight of the FIG. 1. Referring to FIG. 1 andFIG. 2, the balance shaft 40 includes a balance weight 60 that is formedoutside to compensate NVH (Noise vibration and harshness) characteristicof two cylinder engine 1.

A drive gear 31 is disposed at one side of the crankshaft 30, and adriven gear 32 is disposed at the balance shaft 40 to be engaged withthe drive gear 310. The drive gear 31 is engaged with the driven gear 32such that the balance shaft 40 rotates according to a rotation of thecrankshaft 30.

Referring to FIG. 1, the engine 1 includes a chamber 50 that is extendedfrom the crank case 20. The balance weight 60 is disposed at the balanceshaft 40 to connect or disconnect the chamber 50 with the crank case 20.

FIG. 3 is a cross-sectional view showing a condition that a pistondescends in an engine shown in the FIG. 1. Referring to FIG. 3, if thecrankshaft 30 rotates by the up and down movement of the piston 12, thebalance shaft 40 rotates through the drive gear 31 and the driven gear32 to improve a NVH characteristic through a balancing function of thebalance weight 60.

At the same time, the balance weight 60 of the balance shaft 40 controlsthe fluid communication of the chamber 50 with the crank case 20.Accordingly, the variation pressure that is formed in the crank case 20according to the phase difference of the piston 12 can be absorbed bythe chamber 50.

FIG. 4 is a perspective view showing a condition that a balance weightis disposed in a chamber. Referring to FIG. 4, the chamber 50 isconnected to the crank case 20 through the inlet 51 to correspond to thebalance shaft 40 such that the balance shaft 40 opens/closes the inlet51.

The balance weight 60 is mounted on an external circumference of thebalance shaft 40 to have a half circle shape along an exteriorcircumference of the balance shaft 40. Accordingly, while the balanceshaft 40 rotates, the balance weight 60 closes or opens the inlet 51.

That is, as shown in FIG. 3, while the balance weight 60 becomes distantfrom an inlet 51, the balance shaft 40 is exposed to the inlet 51. Inthis case, because the balance weight 60 opens the inlet 51, the chamber50 communicates with the crank case 20 through the inlet 51.

Also, the balance weight 60 has an equal radial width (W, FIG. 1) alongan exterior circumference of the balance shaft 40. That is, the balanceweight 60 has an equal size in a diameter direction along the exteriorcircumference of the balance shaft 40 such that the inlet 51 is closedwhile the balance weight 60 contacts the inlet 51.

Referring to FIG. 4, the chamber 50 is formed in a length direction ofthe crankshaft 30 to be connected to the crank case 20 corresponding tothe crank case 20. The inlet 51 is formed between the chamber 50 and thecrank case 20 in a length direction of the balance shaft 40 disposedparallel to the crankshaft 30. The balance weight 60 is disposed on theinlet 51 in a length direction of the balance shaft 40 corresponding tothe inlet 51.

FIG. 5 to FIG. 8 show operational states of a balance weight in aninlet. As shown in FIG. 5, when the piston 12 is at a top dead center,the balance weight 60 disposed on the balance shaft 40 completely closesthe inlet 51. Accordingly, a pressure loss that is formed during therise of the piston 12 is minimized in the crank case 20. The crank case20 can minimize a pressure loss by reducing a pressure variation volumeas much as that of the chamber 50.

As shown in FIG. 6, if the piston 12 descends from the top dead center,the balance weight 60 of the balance shaft 40 rotates to start openingthe inlet 51. Accordingly, the pressure within the crank case 20 thatstarts to be formed during the descent of the piston 12 is absorbed bythe chamber 50 through the inlet 51.

As shown in FIG. 7, while the piston 12 is positioned at a bottom deadcenter, the balance weight 60 of the balance shaft 40 completely opensthe inlet 51. Accordingly, the pressure within the crank case 20 that isformed during the descent of the piston 12 is absorbed by the chamber 50through the inlet 51. A pressure variation volume is increased as muchas that of the chamber 50 such that the crank case 20 effectivelyabsorbs the pressure variation.

As shown in FIG. 8, when the piston 12 is positioned at a bottom deadcenter, the balance weight opens the inlet 51, and while the balanceshaft 40 is being rotated, the balance weight 60 of the balance shaft 40starts to close the inlet 51. Accordingly, the pressure loss within thecrank case 20 that starts to be formed during the rise of the piston 12starts to be cut off by the balance weight 60.

As described above, an exemplary embodiment of the present inventionincludes the chamber 50 that is formed at one side of the crank case,wherein the inlet 51 of the chamber 50 is opened/closed by the balanceweight 60 to suppress a pressure within the crank case 20 such that theblow by gas is effectively circulated to the intake system withoutenlarging the crank case 20 or a blow by passage.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

1. An engine having a crank case of a variable volume, comprising: acrankshaft that is disposed in a crank case and is connected to a pistonthrough a connecting rod, which reciprocate in a cylinder; a balanceshaft that is disposed in the crank case and is operated by thecrankshaft; a chamber that is extended from the crank case; and abalance weight that is formed on the balance shaft and selectively opensor closes a fluid communication between the chamber and the crank caseaccording to a position of the piston.
 2. The engine having the crankcase of the variable volume of claim 1, wherein the crankshaft includesa drive gear and the balance shaft includes a driven gear that isengaged with the drive gear.
 3. The engine having the crank case of thevariable volume of claim 1, wherein the chamber is fluid-connected tothe crank case through an inlet, the balance shaft is disposed at a sideof the inlet, and the balance weight is formed to have a half circleshape along an exterior circumference direction of the balance shaft. 4.The engine having the crank case of the variable volume of claim 3,wherein the balance weight has an equal radial width along the exteriorcircumference of the balance shaft to rotatably contact with the inlet.5. The engine having the crank case of the variable volume of claim 3,wherein the chamber is disposed in a length direction of the crankshaftto be connected to the crank case, the inlet is formed between thechamber and the crank case in a length direction of the balance shaft,and the balance weight is disposed in a length direction of the balanceshaft corresponding to the inlet.
 6. The engine having the crank case ofthe variable volume of claim 1, wherein the fluid communication betweenthe chamber and the crank case is closed when the piston is at a topdead center.
 7. The engine having the crank case of the variable volumeof claim 1, wherein the fluid communication between the chamber and thecrank case opens when the piston is at a bottom dead center.